1. Field of the Invention
The present invention relates to a plasma display panel (PDP), and in particular to a plasma display panel having a closed delta cell structure and an electromagnetic interference (EMI) device.
2. Description of the Related Art
In a PDP, high voltage through a low pressure gas produces a large magnetic field, thus generating light. The electromagnetic emissions from the magnetic field are governed by Class A and Class B limits of Federal Communications Commission (FCC) standards. Thus, the PDP must be designed in compliance with FCC EMI testing and verification. In the U.S., the FCC requires compliance with Class A for PDP operated in industrial settings and Class B—the stricter standard—in PDP for home use. Additionally, due to high manufacturing costs, most conventional PDPs are designed for industry use.
Due to rapid development of the PDP market in recent years, manufacturing costs have decreased, and particularly when residential space is limited, PDP has gradually become a popular display apparatus. However, PDP meeting FCC EMI Class A is inadequate for home use since the high EMI current of the PDP may interfere with other household appliances such as a home stereo system. Additionally, high EMI level is harmful to health. Thus, home-use PDP must also meet the Class B requirement.
FIG. 1 is a schematic diagram showing an internal structure of a conventional PDP 100′. The conventional PDP 100′ comprises a filter substrate 10′, a front panel 20′ and a rear panel 30′. The filter substrate 10′ is disposed on the exterior edge of the PDP 100′, above the front panel 20′. The rear panel 30′ is disposed at the bottom position of FIG. 1. The filter substrate 10′ and the front panel 20′ are connected by a frame (not shown here) with a gap 15′ therebetween.
The front panel 20′ includes a front glass 22′, a pair of transparent electrodes 24′, a bus electrode 26′, a dielectric layer 25′ and a protective layer 28′. The rear panel 30′ includes phosphor 33′, barrier ribs 31′, a second dielectric layer 34′, a pair of address electrodes 35′ and a second substrate 36′. The barrier rib 31′ is formed above the address electrodes 35′ of the rear panel 30′. Many barrier ribs 31′ constitute a discharge region or cell. The conventional PDP 100′ can be implemented with different cell structures, such as a strip-cell structure, a grid-cell structure, and the delta-cell structure.
The filter substrate 10′ not only protects the panel from damage, but also blocks infrared rays to improve optical performance and prevent electromagnetic interference. The filter substrate 10′ has two types of structure. As shown in FIG. 2A, the first filter substrate 10a′ comprises an anti-reflection film 12′ (hereinafter called the “AR film”), an EMI mesh film 11a′, a glass substrate 23′, and a near-infrared radiation (NIR) film 14′. The EMI mesh film 11a′ is an etching or conductive mesh film. The EMI mesh film 11a′ and other films are disposed on both sides of the glass substrate 23′. Next, the filter substrate 10′ is disposed on the front panel 20′ with a gap 15′ between the filter substrate 10′ and the front panel 20′, as shown in FIG. 1. The AR film 12′ reduces light reflection from the outside and absorbs infrared ray for better optical performance.
The EMI mesh film 11a′ of the first filter substrate 10a′ is only applicable for the strip- or grid-cell structure type PDP. The delta cell structure, especially the closed type, is the most advanced cell structure. If the EMI mesh film 11a′ is disposed in a PDP with closed-type delta cell structure, the EMI mesh film 11a′ acts as an optical grating, producing an adverse effect of visible lines on the display, interfering with users. As a result, if the conventional filter substrate 10′ is disposed in the PDP with closed-type delta cell structure, the PDP cannot pass Class B standards, and its display quality further suffers.
FIG. 2 is a schematic diagram showing another filter device 10b′ with a glass substrate 24′ and a silver (Ag) or indium tin oxide (ITO) sputtered thin film disposed thereon. Conventional filter device 10b′ may comprise ITO film. However, a more recently developed filter device 10b′ has silver sputtered film disposed on the glass substrate 23′ for better EMI and NIR blocking ability.
Generally, neither the resistance of silver nor ITO is high enough for sufficient EMI shielding. For example, ITO film has a low resistance of 150Ω. If the film is thicker, despite improved blocking ability, light penetration ability is decreased. Also, the PDP may only meet FCC Class A requirement, not FCC Class B. Thus, since the conventional EMI mesh film insufficient for blocking electromagnetic waves, the PDP with such EMI film is inappropriate for domestic use.
As mentioned above, PDP requires EMI mesh film to be disposed on a glass substrate 23′, and in a PDP with delta cell structure, use of the conventional EMI mesh film may only meet FCC Class A requirements. Hence, there is a need for a modified EMI mesh film for PDP, according to different cell structures, which can meet both FCC Class A and B requirements and improve display quality.